1. Field of the Invention
The invention relates to a time-division multiplex signal transmission, system comprising a transmitter which includes a power amplifier having a control input supplied with a control voltage, for amplifying a high-frequency input signal. A detector detects the power of the output signal, the detector voltage representing the sum of a detector quiescent voltage and an actual detected voltage. The invention furthermore relates to a transmitter and a control circuit used in such a transmission system.
The transmission system may, for example, be a mobile radio system according to the GSM standard. Such a system operates in the Time-Division Multiple Access (TDMA) mode.
2. Description of the Related Art
European Patent Application 0 462 773 A2 shows a control circuit for controlling the transmitter power in a TDMA system. A detector feeds back part of the transmitted power to a control input via a differential amplifier. This arrangement controls the level of the transmitter power. A signal applied to another control input of the power amplifier controls the form of the rise and fall of the transmitter power at the beginning and end of a time slot. In circuits of this type problems of stability occur when stringent requirements are made on the waveform of the transmitter power and on the permissible spectral range--such as, for example, in the GSM specifications. Furthermore, temperature dependence of the detector forms an obstruction to the capability of the circuit to operate.